The PALE YELLOW box contains: byte 3) MOSI: A NOP command. MISO: The bytes seen at the receiving end of MOSI 15.5 cycles ago byte 4) MOSI: A NOP command. MOSI: The contents of the register (is 0x00, should be 0x01)

The GRAY box is the area magnified in picture two,

I would be most grateful for any suggestions what might be the cause of the problem.

edit: thought of a few things that may be useful to know

I have set the HIGH logic threshold of the logic analyser to 3.5V. This is the threshold for the MAX7301, so the dip in MOSI observed isn't necessarily 0V. In fact, my oscilloscope shows that the LOW signal is a dip to just below ~3.5V.

I have set the HIGH logic threshold of the logic analyser to 3.5V. This is the threshold for the MAX7301, so the dip in MOSI observed isn't necessarily 0V. In fact, my oscilloscope shows that the LOW signal is a dip to just below ~3.5V.